Hip resurfacings revised for inflammatory pseudotumour have a poor outcome

Hip resurfacing arthroplasty reduces dislocation and infection rates without differences in clinical outcomes compared to short and standard stems: A Network Meta-Analysis

BACKGROUND

Total hip arthroplasty (THA) and hip resurfacing arthroplasty (HRA) are established treatments for hip osteoarthritis. Recent advancements have introduced short-stem THA, which offers potential advantages in terms of bone preservation and biomechanical restauration. None of previous studies compared these three surgical interventions. The aim of this network meta-analysis (NMA) is to compare HRA, short stem and standard stem in THA in terms of: (1) complications rate (global, infection and dislocation rate), (2) clinical outcomes (WOMAC, Harris Hip Score (HHS), Oxford Hip Score (OHS), Forgotten Joint Score (FJS), Postel Merle Aubigné Score (PMA) and SF-36) at short- and mid-term, (3) procedure-related variables (operative time, pain at day one and length of stay).

METHODS

A systematic literature review was conducted using multiple electronic databases (Medline, Central and Embase) to identify comparative studies evaluating at least two of the three surgical interventions. Studies were included if they reported one of our outcomes. Data synthesis was performed using a Bayesian NMA. A total of 72 studies including, 793 593 patients (mean age 54.7 years), met the inclusion criteria. The most common comparison was standard-stem THA/ HRA (94,4% of the studies).

RESULTS

The NMA did not identify differences for the rate of global complications between short stem THA/standard-stem THA (risk ratio (RR) 1.52 [95% CI 0.41-5.96]), HRA/standard-stem THA (RR 1.17 [95% CI 0.85-1.66]) and HRA/short-stem THA (RR 0.77 [95% CI 0.20-2.95]). Regarding infection and dislocation, standard THA had a higher rate of infection (risk ratio 2.14 [95% CI 1.33-5.44]) and of dislocation (risk ratio 13.45 [95% CI 3.37-98.21]) compared to HRA. For functional outcomes at short term, no differences were observed between HRA and standard-stem THA for WOMAC (Mean Difference (MD) -0.01 [95% CI -0.51 to 0.40]), HHS (MD 0.05 [95% CI -3.26 to 3.45]), PMA (MD -0.13 [95% CI -0.94 to 0.71]) and FJS (MD -1.64 [95% CI -9.04-5.45]). For functional outcomes at mid-term, no differences were observed between HRA and standard-stem THA for WOMAC (MD -0.07 [95% CI -1.13 to 1.05]), HHS (MD -0.02 [95% CI -1.55 to 1.36]), PMA (MD -0.03 [95% CI -0.60 to 0.49]) and SF-36 (MD 0.11 [95% CI -3.37 to 3.61]). No difference was observed for comparison of short-stem THA/standard-stem THA and HRA/short-stem THA for clinical outcomes.The surgical time was shorter for HRA compared to short-stem THA (MD-34.05 [95% CI -53.25 to -13.28]) and standard-stem THA (MD -16.25 [95% CI -24.84 to -7.53]). No difference was observed between HRA and standard-stem THA for VAS at day one (MD 0.22 [95% CI -1.90 to 2.13]) and for the length of stay (MD 0.48 [95% CI -0.27 to 1.34]).

CONCLUSION

HRA demonstrated had lower infection and dislocation rate compared to standard THA. HRA also offers a shorter operative time. However, no difference was observed for functional outcome between the three technics. These findings support the notion that the choice of technique should be tailored to patient-specific characteristics, highlighting the potential shift towards personalized hip arthroplasty.

LEVEL OF EVIDENCE

III; Network meta-analysis.

Metal Release in Total Knee Arthroplasty: A Review of Mechanisms, Adverse Local Tissue Reactions, and Biological Effects

Compared to the hip, where investigators associate metal release with adverse local tissue reactions (ALTRs), metal-related complications in total knee arthroplasty (TKA) remain controversial and underexplored. Primary TKA systems use monobloc components, limiting corrosion and subsequent concerns. However, like the joints they replace, metal components degrade in vivo. In this narrative review, we aimed to summarize clinically relevant knowledge on metal release within the context of TKA for practicing orthopaedic surgeons. We asked: do ALTRs associated with metal release occur in the knee, and if so, to what extent? To answer this research question, we identified in vivo degradation mechanisms, including wear, mechanically assisted crevice corrosion, and electrocautery damage. Next, we synthesized case reports and retrospective clinical studies documenting ALTRs in primary and revision TKAs. Then, we reviewed the biological response to cobalt chrome debris, focusing on genotoxicity, immune responses, and hypersensitivity. While clinical evidence suggests that patients rarely experience severe biological reactions like pseudotumors, ALTRs associated with metal release can and do occur following TKA. To overcome knowledge gaps related to the prevalence of ALTR in TKA, prospective clinical trials are needed.

Outcomes and Survival of a Single Model of Modular Neck Primary Total Hip Arthroplasty at a Mean of Eight Years

BACKGROUND

We report the outcomes and survival of a recalled modular neck primary total hip arthroplasty (THA). This study's purpose was to describe the survival, complications, patient-reported outcome measures, and serum metal ion levels at a mean of 8 years.

METHODS

We identified 89 hips that received a modular neck THA between May 2010 and March 2012. Failure was defined as the removal of the femoral component for any reason, excluding infection. The patient-reported outcome measures, including the Western Ontario and McMaster Universities Arthritis Index, Harris Hip Score (HHS), and Veterans RAND 12 Physical and Mental Score, and serum metal ion levels were recorded and compared between unrevised and revised patients.

RESULTS

The mean time to the most recent follow-up and revision surgery was 7.79 and 4.31 years, respectively. The mean survivorship was 10.0 years, with a survival of 51% at 13 years. There were 33 infection-free failures identified, with symptomatic adverse local tissue reaction or pseudotumor being the most common (62.5%). Of the patients who underwent revision surgery, six required repeat revisions. When comparing unrevised and revised cases, the unrevised group had significantly greater HHS function (P = 0.002), HHS total (P = 0.003), and Veterans RAND 12 Physical (P = 0.04) scores. Metal ion analysis showed that the mean serum Cobalt ion levels were significantly higher for the revised patients compared to the unrevised patients (P < 0.001).

CONCLUSIONS

This study demonstrated that the taper corrosion-related failure continues to be an issue with this specific modular neck primary THA implant. Functional data demonstrated poorer outcomes in patients who required revision and a following revision surgery compared to patients who did not require a revision surgery. Patients who have received this implant should continue to be monitored on a routine basis, and care providers should have a low threshold to investigate symptoms.

LEVEL OF EVIDENCE

IV.

Are We Ready for Pseudotumors in Total Ankle Arthroplasty? A Case Report

Background: Pseudotumors are defined as exuberant non-neoplastic inflammatory masses. This condition can be associated with hip and knee arthroplasty but has not been reported in Total Ankle Arthroplasty (TAA). This paper reports a pseudotumor that formed following TAA, highlighting its clinical presentation, management, and histopathology. Methods: A 55-year-old male with end-stage post-traumatic ankle osteoarthritis underwent TAA using a mobile-bearing prosthesis. The procedure was reported to be successful, with no immediate complications. Results: Three years postoperatively, following a period of symptom resolution, the patient presented with progressively worsening ankle pain, swelling, and limited weight-bearing ability. Imaging revealed indirect signs of a periarticular mass and loosening components. Revision surgery involved prosthesis explantation and mass excision for histological and microbiological analysis, followed by concomitant tibio-talo-calcaneal fusion with a retrograde nail. The histopathology identified a pseudotumor characterized by chronic inflammation, fibrous tissue, and necrotic debris, with no evidence of infection. The postoperative recovery was uneventful, with pain resolution and successful fusion confirmed at a one-year follow-up. Conclusions: In patients experiencing unexplained pain or symptoms following TAA, the possibility of a pseudotumor, although rare, should be considered. Prompt and comprehensive clinical and radiographic evaluation is crucial to raise suspicion and prevent this condition from being overlooked.

Association between oxidative balance score and serum cobalt level in population with metal implants: a cross-sectional study from NHANES 2015-2020

Background

Growing evidence indicates that metal implants influence the body's oxidative stress status, which in turn affects the degradation and stability of metal implants. The oxidative balance score (OBS) is a composite indicator, reflecting the overall oxidative balance of pro-and antioxidants of the human body. However, the associations between OBS and the level of metal ions on the population with metal implants remain to be elucidated.

Methods

We conducted a cross-sectional study using data from 2015 to 2020 National Health and Nutrition Examination Survey (NHANES). Dietary and lifestyle factors closely associated with oxidative stress were quantified to calculate the OBS. Weighted multivariate logistic regression and smooth curve fittings were performed to examine the relationship between OBS and serum cobalt levels. Subgroup analyses were stratified by age and gender. In cases where non-linearity was detected, threshold effects were assessed using a two-piecewise linear regression model.

Results

A total of 549 participants were included in this analysis. The dietary OBS was negatively associated with serum cobalt level in fully adjusted model (β = -0.179, 95%CI: -0.358 to -0.001, P: 0.04918). Stratified by age and gender, negative correlation of OBS and dietary OBS with serum cobalt level was observed only in men and age over 70 years participants. Threshold effect analysis showed linear relationships between OBS, dietary OBS and cobalt level in males. There were non-linear relationships between OBS, dietary OBS and cobalt level in age over 70 years participants, with inflection points identified at 16.3 and 8.7 for OBS and dietary OBS, respectively.

Conclusion

Our study confirms the inverse relationships between oxidative stress and serum cobalt level in individuals with metal implants, highlighting the significance of optimizing OBS to mitigate the risk of metal ion toxicity. These findings emphasize the importance of maintaining an antioxidant diet and lifestyle, particularly as they offer greater protective effect for males and the elderly population.

Conversion of hip resurfacing to total hip arthroplasty: is the outcome closer to primary or revision total hip arthroplasty?

BACKGROUND

Along with the advent of newer bearings, hip resurfacing (HR) is gaining renewed interest as a bone sparing alternative to conventional total hip arthroplasty (THA) in young patients. However, the outcome of conversion of failed HR to THA (HRc) remains sparsely described. This study aimed to compare the outcomes and complication rates of HRc to those of primary (pTHA) and revision THA (rTHA) to find out to which group HRc is most comparable.

HYPOTHESIS

The study hypothesis was that the outcomes and complications rates of HRc were closer to those of pTHA than rTHA.

MATERIALS AND METHODS

Between 2001 and 2011, a continuous series of 207 HR were prospectively included in our institutional registry and retrospectively analyzed. Out of them, 17 HR (8%) were converted to THA. Propensity scores were used to match patients in the HRc group to the pTHA and the rTHA groups using a greedy 1:3 matching procedure (51 pTHA and 51 rTHA). Clinical and radiographic outcomes, perioperative data and complications were analyzed and compared between the three groups.

RESULTS

No significant difference between HRc and pTHA was observed in terms of clinical and functional outcomes, duration of surgery, acetabular component diameter and length of hospital stay (p = 0.13 to 0.94). Perioperative blood loss was significantly lower for pTHA than for HRc (p = 0.01). HRc demonstrated significantly higher HHS and HOOS scores than for rTHA at one year (p = 0.03 and p < 0.01, respectively). Duration of surgery was significantly lower in HRc compared to rTHA (p = 0.02) while length of hospital stay was similar (p = 0.84). Complication rate was significantly higher in the rTHA group, compared to HRc and pTHA groups (37.3 vs. 29.4 vs. 11.8%, p = 0.01).

CONCLUSION

This study demonstrated that the clinical and functional outcomes of HRc were closer to those of pTHA than those of rTHA, though complication rate was higher than for pTHA.

LEVEL OF EVIDENCE

III; Retrospective comparative study.

Predicting extended hospital stay following revision total hip arthroplasty: a machine learning model analysis based on the ACS-NSQIP database

INTRODUCTION

Prolonged length of stay (LOS) following revision total hip arthroplasty (THA) can lead to increased healthcare costs, higher rates of readmission, and lower patient satisfaction. In this study, we investigated the predictive power of machine learning (ML) models for prolonged LOS after revision THA using patient data from a national-scale patient repository.

MATERIALS AND METHODS

We identified 11,737 revision THA cases from the American College of Surgeons National Surgical Quality Improvement Program database from 2013 to 2020. Prolonged LOS was defined as exceeding the 75th value of all LOSs in the study cohort. We developed four ML models: artificial neural network (ANN), random forest, histogram-based gradient boosting, and k-nearest neighbor, to predict prolonged LOS after revision THA. Each model's performance was assessed during training and testing sessions in terms of discrimination, calibration, and clinical utility.

RESULTS

The ANN model was the most accurate with an AUC of 0.82, calibration slope of 0.90, calibration intercept of 0.02, and Brier score of 0.140 during testing, indicating the model's competency in distinguishing patients subject to prolonged LOS with minimal prediction error. All models showed clinical utility by producing net benefits in the decision curve analyses. The most significant predictors of prolonged LOS were preoperative blood tests (hematocrit, platelet count, and leukocyte count), preoperative transfusion, operation time, indications for revision THA (infection), and age.

CONCLUSIONS

Our study demonstrated that the ML model accurately predicted prolonged LOS after revision THA. The results highlighted the importance of the indications for revision surgery in determining the risk of prolonged LOS. With the model's aid, clinicians can stratify individual patients based on key factors, improve care coordination and discharge planning for those at risk of prolonged LOS, and increase cost efficiency.

Examining the "revisability" benefit of hip resurfacing arthroplasty

BACKGROUND

Hip resurfacing arthroplasty (HRA) is an alternative to total hip arthroplasty (THA) that is typically reserved for young active patients because it preserves bone. However, the benefits of HRA only hold true if conversion THA after failed HRA provides acceptable outcomes.

AIM

To compare patient reported outcomes for conversion THA after HRA failure to primary THA.

METHODS

A retrospective review of 36 patients (37 hips) that underwent conversion THA for failed HRA between October 2006 and May 2019 by a single surgeon was performed. Patient reported outcomes [modified Harris Hip Score (mHHS), University of California Los Angeles (UCLA) activity score] were obtained via an email-based responder-anonymous survey. Outcomes were compared to normative data of a primary THA cohort with similar demographics. Subgroup analysis was performed comparing outcomes of conversion THA for adverse local tissue reaction (ALTR) vs all other causes for failure.

RESULTS

The study group had a lower mHHS than the control group (81.7 ± 13.8 vs 90.2 ± 11.6, P < 0.01); however, both groups had similar UCLA activity levels (7.5 ± 2.3 vs 7.2 ± 1.6, P = 0.51). Patients that underwent conversion for non-ATLR causes had similar mHHS (85.2 ± 11.5 vs 90.2 ± 11.6, P = 0.11) and higher UCLA activity levels (8.5 ± 1.8 vs 7.2 ± 1.6, P < 0.01) compared to the control group. Patients that underwent conversion for ATLR had worse mHHS (77.1 ± 14.5 vs 90.2 ± 11.6, P < 0.01) and UCLA activity levels (6.1 ± 2.3 vs 7.2 ± 1.6, P = 0.05) when compared to the control group.

CONCLUSION

Patient outcomes equivalent to primary THA can be achieved following HRA conversion to THA. However, inferior outcomes were demonstrated for ALTR-related HRA failure. Patient selection and perhaps further studies examining alternative HRA bearing surfaces should be considered.

Outcome of hip resurfacing revision through the Hueter-anterior approach

BACKGROUND

The Hueter-Anterior Approach (HAA) with its limited soft tissue and internervous dissection has been shown to be an effective approach for primary total hip and hip resurfacing arthroplasty (HRA). The purpose of this study is to evaluate the clinical outcome of patients requiring revision of HRA to total hip replacement using the HAA, assessing function and complications.

METHODS

We performed a retrospective review of a prospectively maintained research database. Between 2006 and 2015, 555 primary metal-on-metal (MoM) HRAs were performed via the HAA; we identified 33 hips in 30 patients that required revisions for aseptic causes to THA: aseptic loosening of acetabulum in 12 and femoral in 7, 10 for pseudotumour/ALTR, 4 for femoral neck fracture. All revision surgeries were performed through a HAA by a single surgeon who had also performed the index operation. PROMs were collected preoperatively and yearly at various timepoints postoperatively.

RESULTS

The mean age at time of revision was 48.9 years (±5.3 SD) for 22 males (67%) and 11 females (33%). The mean time to revision surgery/failure of hip resurfacing was 3.3 years (±2.4 SD). There were 5 major reoperations with 3 infections, 1 acetabular loosening and 1 trunnionosis. There were significant improvements in multiple PROMs.

CONCLUSIONS

The HAA is a viable surgical approach for revision of HRA with smaller initial HRA acetabular components generally requiring a relatively larger acetabular compoent at time of revision. Patients reported improvement in symptoms and function and a lower risk of subsequent reoperation than what has previously been reported for failed MoM bearings.

The use of dual mobility cups in revision total hip arthroplasty for failed large head metal-on-metal bearings

PURPOSE

Revision of failed large head metal-on-metal (MoM) total hip arthroplasty (THA) is a challenging procedure particularly to reconstruct acetabular bone defect due to osteolysis and to achieve hip stability due to soft tissue damages, both potentially caused by adverse reaction to metal debris (ARMD). This study aimed to evaluate the outcome of dual mobility cup (DMC) constructs in revision THA for failed large head MoM bearings with a special attention to the occurrence of dislocation or re-revision.

METHODS

Between 2015 and 2019, 57 patients (64 THAs, 41 men, mean age = 65 ± 10 years) underwent revision for MoM THA with the use of DMC were prospectively included in our total joint registry. Mean time to revision was 11 ± 2.5 years. The causes for revision were adverse reaction to metal debris (ARMD) in 49 THAs (76%), painful hip with elevated blood cobalt-chromium ions in seven (11%), and acetabular aseptic loosening in eight (13%). The revision was complete in 22 THAs (34%) and acetabular only in 42 (66%). Clinical and radiographic outcomes, complications, and re-revisions were evaluated at most recent follow-up.

RESULTS

At mean follow-up of six ± 1.5 years, the pre- to postoperative Harris Hip Score improved from 74 ± 19 to 92 ± 4 (p = 0.004). Complications occurred in 11 cases (17%): five dislocations (8%), three periprosthetic infections (5%), two aseptic loosening of the acetabular component (3%), and two periprosthetic fractures (3%). Re-revision was required in six cases (9%).

CONCLUSION

The use of DMC is a reliable option to prevent instability and ensure a stable acetabular reconstruction in revision THA for failed large head MoM bearings. However, dislocation after revision remains a concern, particularly in cases of severe soft tissue damage related to ARMD.

Cobalt and Chromium Ions Impair Macrophage Response to Staphylococcus aureus Infection

Cobalt-chromium-molybdenum (CoCrMo) alloys are routinely used in arthroplasty. CoCrMo wear particles and ions derived from arthroplasty implants lead to macrophage-driven adverse local tissue reactions, which have been linked to an increased risk of periprosthetic joint infection after revision arthroplasty. While metal-induced cytotoxicity is well characterized in human macrophages, direct effects on their functionality have remained elusive. Synchrotron radiation X-ray microtomography and X-ray fluorescence mapping indicated that peri-implant tissues harvested during aseptic revision of different arthroplasty implants are exposed to Co and Cr in situ. Confocal laser scanning microscopy revealed that macrophage influx is predominant in patient tissue. While in vitro exposure to Cr3+ had only minor effects on monocytes/macrophage phenotype, pathologic concentrations of Co2+ significantly impaired both, monocyte/macrophage phenotype and functionality. High concentrations of Co2+ led to a shift in macrophage subsets and loss of surface markers, including CD14 and CD16. Both Co2+ and Cr3+ impaired macrophage responses to Staphylococcus aureus infection, and particularly, Co2+-exposed macrophages showed decreased phagocytic activity. These findings demonstrate the immunosuppressive effects of locally elevated metal ions on the innate immune response and support further investigations, including studies exploring whether Co2+ and Cr3+ or CoCrMo alloys per se expose the patients to a higher risk of infections post-revision arthroplasty.

Long-Term Outcomes of Birmingham Hip Resurfacing Arthroplasty: A Systematic Review of Independent Series with At Least 10 Years of Follow-up

Background

Hip resurfacing arthroplasty (HRA) provides an attractive alternative to total hip arthroplasty (THA) for the management of osteoarthritis in younger, more active patients; however, concerns persist over complications specific to HRA. The aims of this systematic review were to assess the documented long-term survival rates of the metal-on-metal BIRMINGHAM HIP Resurfacing System at a follow-up of at least 10 years and to analyze the functional outcomes and cause of failures.

Methods

A systematic review was undertaken of all published cohort studies available in the MEDLINE, Cochrane, Embase, and PubMed research databases up to December 2021, as recommended by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Data extraction was focused on survival rates, causes of failure, and functional outcomes. Survival estimates at 10 years were pooled in a meta-analysis, with each series weighted by its variance. Causes of failure were presented as a percentage of the pooled revisions.

Results

A total of 11 studies were identified, encompassing 3,129 cases. Across the 9 studies that had reported a mean follow-up, the mean follow-up was 11.7 years (range, 9.55 to 13.7 years). We found a pooled 10-year survival rate of 95.5% (95% confidence interval, 93.4% to 97.1%). There were 149 revisions among the studies (range, 4 to 38 revisions per study), a rate of 4.8% of the total procedures performed. The 2 main causes of revision were aseptic loosening (20.1% of revisions) and adverse reactions to metal debris (20.1%). There were no revisions for dislocation. Of the studies that reported preoperative functional scores, all reported significant improvement in mean scores postoperatively except for 1 study in which the mean Tegner activity score did not significantly improve.

Conclusions

When performed for appropriate indications, patients undergoing an HRA with use of the BIRMINGHAM HIP Resurfacing System can expect good implant survivorship at 10 years with acceptable functional results and low rates of dislocation and infection. This systematic review, however, confirms concerns regarding adverse reactions to metal debris as a leading cause of revision.

Level of Evidence

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The anatomical location of cystic pseudotumors and muscle atrophy in metal-on-metal resurfacing hip arthroplasty is related to the surgical approach used for implantation. A subgroup analyses of a randomized controlled trial

BACKGROUND

Pseudotumors and muscle atrophy have been associated with metal-on-metal (MoM) resurfacing hip arthroplasty (RHA). We aimed to investigate the influence of the anterolateral (AntLat) and the posterior (Post) surgical approach on the location, grade and prevalence of pseudotumors and muscle atrophy in MoM RHA.

PATIENTS AND METHODS

Forty-nine patients were randomized to MoM RHA by the AntLat (n = 25) or the Post (n = 24) approach at Aarhus University Hospital. Patients underwent metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) scans for investigation of location, grade and prevalence of pseudotumors and muscle atrophy. Plain radiographs, metal-ions concentrations and clinical outcome scores were evaluated to compare outcomes of the surgical approaches.

RESULTS

MRI-detected pseudotumors were seen in 7 of 18 patients (39%) in the AntLat group and in 12 of 22 patients (55%) in the Post group (p = 0.33). Pseudotumors were mainly located anterolaterally to the hip joint in the AntLat group and postero-lateral to the hip joint in the Post group. Higher grades of muscle atrophy of the caudal part of the gluteus medius and minimus (p < 0.004) were seen in the AntLat group, and higher grades of muscle atrophy of the small external rotators were seen in the Post group (p < 0.001). The AntLat group had higher anteversion angles of mean 15.3° (range 6.1-7.5) versus mean 11.5° (range 4.9-22.5) in the Post group (p = 0.02). Metal-ion concentrations and clinical outcome scores were similar between groups (p > 0.08).

CONCLUSION

Muscle atrophy and pseudotumor location after MoM RHA follow the surgical approach used for implantation. This knowledge may help differentiate between "normal postoperative appearance" and "MoM disease."

Midterm results of the Birmingham hip resurfacing: a single-surgeon series

INTRODUCTION

Birmingham hip resurfacing (BHR) is readily used as alternative to total hip replacement in younger patients. The current study aims to compare outcomes in terms of adverse local tissue reactions (ALTR), elevated metal ion levels and survival rates between low-risk (femoral component size ≥ 48 mm) and high-risk (femoral component size < 48 mm) BHR patients at a minimum 5-year follow-up (FU).

MATERIALS AND METHODS

We report the minimum 5-year, single surgeon outcome results of 183 BHRs, performed between 2007 and 2012. 154 patients, 18 women (20 hips) and 136 men (163 hips) were included in the study. Patients were grouped in 149 low-risk cases (femoral component size ≥ 48 mm) and in 34 high-risk cases (18 female/12 male) patients with a femoral head size < 48 mm).

RESULTS

At a minimum of 5-years FU time, 91% of the patients were available for FU. The overall survival rate was 91.8%. There were five revisions (survival rate 96.6%) in the low-risk group and ten revisions (survival rate 70.6%) in the high-risk group. In the low-risk group, six patients (6.5%) showed elevated metal ion levels (> 7 μg/l), compared to five patients (20.8%) in the high risk-group (p = 0.03).

CONCLUSION

Including the surgeon's initial learning curve, the BHR shows very good mid-term survival rates in the low-risk group but should, as previously demonstrated, not be considered for patients with less than 48 mm femoral head size.

LEVEL OF EVIDENCE

Level III: retrospective cohort study.

[Postoperative outcomes and survival rates after aseptic revision total hip arthroplasty : What can patients expect from revision surgery?]

BACKGROUND

In 2020, more than 14,000 aseptic revision procedures for total hip arthroplasty (THA) were registered in Germany. Patient expectations of revision hip arthroplasty are not substantially different from expectations of primary hip replacement.

OUTCOME

However, revision surgery is associated with increased complication rates and a higher proportion of dissatisfied patients. In particular, poorer postoperative function and mobility as well as increased pain levels following revision THA have been described compared to the outcome after primary THA. Quality of life and return-to-work can also be impaired.

SURVIVAL RATE

Implant survival is influenced by age, BMI, and comorbidities of the patients, but also by the size and complexity of bone defects, the extent of periprosthetic soft tissue compromise and the choice of revision implant(s). In addition, the number of previous revision surgeries inversely correlates with the survival rates. Previous revisions have been shown to be associated with increased risks of aseptic loosening, instability and periprosthetic infection.

Outcome of revised metal-on-metal hip arthroplasties: a Dutch arthroplasty register study

BACKGROUND

Preliminary results of metal-on-metal (MoM) hip arthroplasty were satisfactory, but since 2004 data showed high failure rates. National joint replacement registries are multi-centre databases comprised of thousands of subjects and implants which allow for identifying variables predictive of implant failure. The aim of the current study was to estimate re-revision rates after revision of a primary MoM hip arthroplasty in the Dutch Arthroplasty Register (LROI) and to assess potential predictor variables of re-revision of these MoM hip arthroplasties.

METHODS

Eligible procedures were those with a revision for any reason except infection, after an initial primary surgery with a hip resurfacing (HRA) or large-head MoM (LH-MoM) total hip arthroplasty (THA). The probability of re-revision for both types of MoM hip arthroplasty over time was estimated using the cumulative incidence function taking mortality as a competing risk into account. A proportional sub-distribution hazards regression model was used to assess potential predictor variables of re-revision of these MoM hip arthroplasties.

RESULTS

A total of 3476 records of revised implants were included, of which 873 (25.2%) were MoM implants. Over the course of follow-up, 101 (11.5%) MoM implants were re-revised. During follow-up 36 (4.3%) patients who received a MoM-implant at primary arthroplasty and a revision afterwards had died. The regression model showed that for primary MoM implants a MoM articulation after revision (HR 2.48; 95% CI 1.53-4.03, p < 0.001), femoral-only revisions (HR 3.20; 95% CI 2.06-4.99, p < 0.001) and periprosthetic fractures (HR 1.98; 95% CI 1.03-3.82, p = 0.042) as reason for the first revision were statistically significant risk factors for re-revision.

CONCLUSION

Both types of large-head MoM hip arthroplasties have shown high revision and re-revision rates; risk factors were identified. The outcome of this study can be helpful in managing expectations of patients and orthopaedic surgeons.

How much does a Medical and Healthcare Products Regulatory Agency medical device alert for metal-on-metal hip arthroplasty patients really cost?

BACKGROUND

Many worldwide regulatory authorities recommend regular surveillance of metal-on-metal hip arthroplasty patients given high failure rates. However, concerns have been raised about whether such regular surveillance, which includes asymptomatic patients, is evidence-based and cost-effective. We determined: (1) the cost of implementing the 2015 MHRA surveillance in "at-risk" Birmingham Hip Resurfacing (BHR) patients; and (2) how many asymptomatic hips with adverse reactions to metal debris (ARMD) would have been missed without patient recall.

METHODS

All BHR patients eligible for the 2015 MHRA recall (all females, and males with head sizes ⩽46 mm, regardless of symptoms) at one centre were invited for review (hips = 707; patients = 593). All patients were investigated (Oxford Hip Score, radiographs, blood metal ions, and targeted cross-sectional imaging) and managed accordingly. Surveillance costs were calculated using finance department data.

RESULTS

The surveillance cost £105,921.79 (range £147.76-£257.50/patient). Radiographs (£39,598) and nurse practitioner time/assistance (£23,618) accounted for 60% of overall costs. 31 hips had ARMD on imaging (12 revised; 19 under surveillance). All revisions were symptomatic. 7 hips with ARMD under surveillance were asymptomatic and remain under regular review. The number needed to treat to avoid missing one asymptomatic ARMD case was 101 patients, representing a cost of £18,041 to avoid one asymptomatic case.

CONCLUSIONS

Implementing MHRA surveillance for "at-risk" BHR patients was extremely costly. The risk of asymptomatic ARMD was low with the BHR (1%), suggesting recommended follow-up in asymptomatic patients is not cost efficient. This raises concerns about the increasingly intensive surveillance recommended in the 2017 MHRA guidance for metal-on-metal hip patients.

The influence of HLA genotype on the development of metal hypersensitivity following joint replacement

Background

Over five million joint replacements are performed across the world each year. Cobalt chrome (CoCr) components are used in most of these procedures. Some patients develop delayed-type hypersensitivity (DTH) responses to CoCr implants, resulting in tissue damage and revision surgery. DTH is unpredictable and genetic links have yet to be definitively established.

Methods

At a single site, we carried out an initial investigation to identify HLA alleles associated with development of DTH following metal-on-metal hip arthroplasty. We then recruited patients from other centres to train and validate an algorithm incorporating patient age, gender, HLA genotype, and blood metal concentrations to predict the development of DTH. Accuracy of the modelling was assessed using performance metrics including time-dependent receiver operator curves.

Results

Using next-generation sequencing, here we determine the HLA genotypes of 606 patients. 176 of these patients had experienced failure of their prostheses; the remaining 430 remain asymptomatic at a mean follow up of twelve years. We demonstrate that the development of DTH is associated with patient age, gender, the magnitude of metal exposure, and the presence of certain HLA class II alleles. We show that the predictive algorithm developed from this investigation performs to an accuracy suitable for clinical use, with weighted mean survival probability errors of 1.8% and 3.1% for pre-operative and post-operative models respectively.

Conclusions

The development of DTH following joint replacement appears to be determined by the interaction between implant wear and a patient's genotype. The algorithm described in this paper may improve implant selection and help direct patient surveillance following surgery. Further consideration should be given towards understanding patient-specific responses to different biomaterials.

Tailoring the dissolution rate and in vitro cell response of silicon nitride coatings through combinatorial sputtering with chromium and niobium

Ceramic coatings have been widely investigated as a means to reduce wear and metallic ion release from joint implants. Silicon nitride-based coatings have been a topic of interest specifically due to their solubility in aqueous solutions. This could imply a reduced adverse immune response since the generated debris would dissolve. However, there are concerns regarding the dissolution rate and adhesion of these silicon nitride-based coatings. This study attempts to address the concern of dissolution rate as well as coating adhesion of silicon nitride coatings. We hypothesized that alloying with chromium and niobium would affect the adhesion, dissolution rate, and the resulting ion release and cell response to the coatings. A combinatorial approach was used to deposit sputtered coatings with compositional gradients both with and without a CrN interlayer. Compositional gradients were achieved for all the investigated elements: Si (38.6-46.9 at%), Nb (2.2-4.6 at%) and Cr (1.9-6.0 at%). However, while the presence of an interlayer reduced the delamination during adhesion testing, the differences in composition in the top coating did not affect the adhesion. Nor did the top coating's composition affect the surface roughness or the coatings' inherent mechanical properties (elastic modulus and hardness). All coating compositions were associated with a low Co release from the underlying metal and points with a higher Cr content (4.3-6.0 at%) gave an overall lower release of Si, Cr and Nb ions, possibly due to the formation of a stable oxide, which reduced the dissolution rate of the coating. Optimum chromium contents were furthermore found to give an enhanced in vitro fibroblast cell viability. In conclusion, the results indicate a possibility to tailor the ion release rate, which lends promise to further investigations such as tribocorrosive tests towards a future biomedical application.

Integrating the Combined Sagittal Index Reduces the Risk of Dislocation Following Total Hip Replacement

BACKGROUND

The aims of this matched cohort study were to (1) assess differences in spinopelvic characteristics between patients who sustained a dislocation after total hip arthroplasty (THA) and a control group without a dislocation, (2) identify spinopelvic characteristics associated with the risk of dislocation, and (3) propose an algorithm including individual spinopelvic characteristics to define an optimized cup orientation target to minimize dislocation risk.

METHODS

Fifty patients with a history of THA dislocation (29 posterior and 21 anterior dislocations) were matched for age, sex, body mass index (BMI), index diagnosis, surgical approach, and femoral head size with 200 controls. All patients underwent detailed quasi-static radiographic evaluations of the coronal (offset, center of rotation, and cup inclination/anteversion) and sagittal (pelvic tilt [PT], sacral slope [SS], pelvic incidence [PI], lumbar lordosis [LL], pelvic-femoral angle [PFA], and cup anteinclination [AI]) reconstructions. The spinopelvic balance (PI - LL), combined sagittal index (CSI = PFA + cup AI), and Hip-User Index were determined. Parameters were compared between the control and dislocation groups (2-group analysis) and between the controls and 2 dislocation groups identified according to the direction of the dislocation (3-group analysis). Important thresholds were determined from receiver operating characteristic (ROC) curve analyses and the mean values of the control group; thresholds were expanded incrementally in conjunction with running-hypothesis tests.

RESULTS

There were no coronal differences, other than cup anteversion, between groups. However, most sagittal parameters (LL, PT, CSI, PI - LL, and Hip-User Index) differed significantly. The 3 strongest predictors of instability were PI - LL >10° (sensitivity of 70% and specificity of 65% for instability regardless of direction), CSIstanding of <216° (posterior instability), and CSIstanding of >244° (anterior instability). A CSI that was not between 205° and 245° on the standing radiograph (CSIstanding) was associated with a significantly increased dislocation risk (odds ratio [OR]: 4.2; 95% confidence interval [CI]: 2.2 to 8.2; p < 0.001). In patients with an unbalanced and/or rigid lumbar spine, a CSIstanding that was not 215° to 235° was associated with a significantly increased dislocation risk (OR: 5.1; 95% CI: 1.8 to 14.9; p = 0.001).

CONCLUSIONS

Spinopelvic imbalance (PI - LL >10°) determined from a preoperative standing lateral spinopelvic radiograph can be a useful screening tool, alerting surgeons that a patient is at increased dislocation risk. Measurement of the PFA preoperatively provides valuable information to determine the optimum cup orientation to aim for a CSIstanding of 205° to 245°, which is associated with a reduced dislocation risk. For patients at increased dislocation risk due to spinopelvic imbalance (PI - LL >10°), the range for the optimum CSI is narrower.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Limited need for screening of metal-on-metal hip resurfacing patients beyond 10 years of follow-up

BACKGROUND

National and international guidelines lack consistency on how to screen metal-on-metal (MoM) hip arthroplasty patients for adverse reactions to metal debris (ARMD). Long-term outcomes of MoM hip arthroplasty are scarce, hindering further development of such guidelines. We present the clinical, radiological and ARMD status of 158 cases of hip resurfacing with >10 years follow-up.

METHODS

A prospective analysis of a cohort of 298 consecutive hip resurfacing procedures was performed at a single institution. All patients underwent MARS-MRI scanning for pseudotumour screening at least once, regardless of symptoms. Implant survival and reasons for revision were analysed for all patients. Clinical, radiological and MARS-MRI results were analysed for 158 unrevised procedures with >10 years follow-up.

RESULTS

The implant survival was 85.9% at 14.5 years (95% CI, 81.9-90.6) with revision for all causes as endpoint and 92.3% with MoM disease-related revisions excluded (95% CI, 88.2-95.0). Of the 158 cases with >10 years follow-up, 1 had elevated metal ion levels, 29 had a stable C1 pseudotumour and 6 a stable C2 pseudotumour. All pseudotumours were observed within 3 years after initiating our intensified ARMD screening (2011), with no new pseudotumours observed after that period.

CONCLUSIONS

We suggest that follow-up of MoM hip resurfacing patients beyond 10 years after surgery can be done with large intervals (i.e. every 5 years), and only earlier if a patient becomes symptomatic.

Adverse Local Tissue Reactions are Common in Asymptomatic Individuals After Hip Resurfacing Arthroplasty: Interim Report from a Prospective Longitudinal Study

BACKGROUND

The evaluation of the natural history prevalence of adverse local tissue reactions (ALTRs) using MRI has focused only on metal-on-metal (MoM) bearing surfaces without comparison to nonMoM bearing surfaces.

QUESTIONS/PURPOSES

To determine (1) the longitudinal changes and differences in blood metal ion levels in patients with hip resurfacing arthroplasty (HRA), ceramic-on-ceramic (CoC) THA, and metal-on-polyethylene (MoP) THA compared with those undergoing ceramic-on-polyethylene (CoP) THA; (2) how the longitudinal change of synovial reaction classification in patients with HRA, CoC THA, and MoP THA compares with those undergoing CoP THA, and whether there is an association between the presence of an ALTR or metallosis on MRI with corresponding patient-reported outcomes, or the presence of capsular dehiscence; and (3) differences in blood metal ion levels between patients undergoing HRA with an ALTR or metallosis on MRI and those with HRA without these conditions.

METHODS

Between March 2014 and February 2019, 22,723 patients underwent primary HRA and THA at one center. Patients received an HRA based on their desired athletic level after surgery and the presence of normal acetabular and proximal femoral bone morphology without osteopenia or osteoporosis. Two percent (342 of 22,723) of patients were contacted to participate, and 71% (243 of 342 hips in 206 patients) were enrolled for analysis at baseline. The patients underwent arthroplasty for degenerative joint disease, and 25 patients withdrew over the course of the study. We included patients who were more than 1 year postarthroplasty. All participants had an MRI examination and blood serum ion testing and completed a Hip Disability and Osteoarthritis Outcome Score survey annually for four years (baseline, year 1, year 2, year 3). Morphologic and susceptibility-reduced MR images were evaluated by a single radiologist not involved in the care of patients for the presence and classification of synovitis (Gwet AC1: 0.65 to 0.97), synovial thickness, and volume (coefficient of repeatability: 1.8 cm3). Linear mixed-effects models were used to compare the mean synovial thickness, synovial volume, and Hip Disability and Osteoarthritis Outcome Score subscales between bearing surfaces at each timepoint and within each bearing surface over time. Marginal Cox proportional hazards models were used to compare the time to and the risk of developing ALTR only, metallosis only, and ALTR or metallosis between bearing surfaces. All models were adjusted for age, sex, BMI, and length of implantation based on known confounders for hip arthroplasty. Adjustment for multiple comparisons was performed using the Dunnett-Hsu method.

RESULTS

Patients with unilateral HRA had higher cobalt and chromium serum ion levels (baseline: 1.8 ± 0.8 ppb, year 1: 2.0 ± 1.5 ppb, year 2: 2.1 ± 1.2 ppb, year 3: 1.6 ± 0.7 ppb) than those with unilateral CoP bearings (baseline: 0.0 ± 0.1 ppb, year 1: 0.1 ± 0.3 ppb, year 2: 0.0 ± 0.2 ppb, year 3: 0.0 ± 0.0 ppb) at all timepoints (p < 0.001 for each time point). More patients who received an HRA developed ALTR or metallosis on MRI than did patients with CoP bearings (hazard ratio 4.8 [95% confidence interval 1.2 to 18.4]; p = 0.02). There was no association between the longitudinal change of synovial reaction to ALTR or metallosis on MRI with patient-reported outcomes. In addition, there was no association between the presence of dehiscence at baseline and the subsequent development of ALTR or metallosis, as seen on MRI. There were elevated cobalt (4.7 ± 3.5 ppb) and chromium (4.7 ± 2.6 ppb) serum levels in patients with unilateral HRA who had an ALTR or metallosis present on MRI at year 1 compared with patients without an ALTR or metallosis on MRI (cobalt: 1.8 ± 1.0 ppb, mean difference 4.7 ppb [95% CI 3.3 to 6.0]; p < 0.001; chromium: 2.3 ± 0.5 ppb, mean difference 3.6 ppb [95% CI 2.2 to 5.0]; p < 0.001) as well as for chromium at year 3 (3.9 ± 2.4 ppb versus 2.2 ± 1.1 ppb, mean difference 1.3 ppb [95% CI 0.3 to 2.4]; p = 0.01).

CONCLUSION

We found a higher proportion of ALTR or metallosis on MRI in patients with HRA compared with patients with CoP, even when patient self-assessed symptomatology of those with an ALTR or metallosis on MRI was not different than the absence of these features. MRI detected ALTRs in high-function patients, emphasizing that an annual clinical assessment dependent on survey or blood ion testing alone may not detect soft tissue complications. The results of this study are in line with prior consensus recommendations of using MRI as part of a routine follow-up protocol for this patient population.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Surgical management of hip prosthetic failure in metallosis: A case series and literature review

Local and remote complications can be observed in hip prosthesis failures associated with metallosis. Structural changes in the periprosthetic bone and soft tissues may not always be precisely assessed preoperatively due to metal artifacts. The unpredictability of the damage extension, potentially leading to complex and insidious surgeries, requires the availability of alternative surgical plan(s) for the reconstruction of the joint. The aim of the study is to present and analyze, with the literature data support, practical tips for the revision of the prosthetic components, the management of ARMD and of intraoperative complications in the unusual scenario of metallosis.

Hueter Anterior Approach for Metal-on-Metal Hip Resurfacing Arthroplasty: 555 Cases at a Minimum Five-Year Follow-Up

BACKGROUND

Purpose of this study was to determine implant survivorship and resultant outcomes, including modes of failure, for metal-on-metal hip resurfacing through the Hueter anterior approach (HAA).

METHODS

Retrospective review of cases from 2006 to 2015, resulted in 555 metal-on-metal hip resurfacing via HAA, mean age 49.4 ± 6.9 years and mean BMI 28.1 ± 5.3. Kaplan-Meier curves were used to assess implant survivorship. Evaluation of technique was based on radiographic assessment of component position at 6 weeks. Patient-reported outcome measures were assessed using 12-Item Short Form Survey 12, University of California Los Angeles activity, Western Ontario and McMaster Universities Osteoarthritis Index, and hip disability osteoarthritis outcome scores.

RESULTS

At a mean follow-up of 9.18 years, survivorship was 95.0% at 5 years (95% CI: 93.2-96.8 years) and 92.5% at 10 years (95% CI: 90.0-95.0 years); men at 96.1% (95% CI: 94.3-97.9) and 93.8% (95% CI: 91.1-96.5), and women at 88.8% (95% CI: 81.9-95.7) and 85.6% (95% CI: 77.6-93.6), 5 and 10 years, respectively (P = .033). There were 37 revisions to total hips (7%) at a mean time of 3.3 years (SD 2.7). Indications for revision were aseptic loosening of acetabular (n = 12) and femoral component (n = 7) and pseudotumor (n = 6). Radiographic parameters were respectable and consistent, median acetabular inclination angle 41.2° and femoral stem shaft angle 137.7°. Patient-reported outcome measure scores significantly improved and remained stable at 2 and 5 years postoperatively.

CONCLUSION

Although choice of surgical approach should always be based on surgeon's technical expertise, this study has shown that HAA is safe and effective for hip resurfacing. Mindful attention to long-term metal ion exposure must still be considered.

Catastrophic failure and metallosis of the acetabular component in total hip arthroplasty

Background

To evaluate the clinical features and results of the revision total hip arthroplasties (THA) in patients with catastrophic failures and metallosis.

Methods

Fifteen hips of 14 patients with catastrophic failure and metallosis in hip arthroplasties were evaluated. They were followed for at least 4.2 years after the revision THA. Clinical evaluation was performed using Harris hip score. Osteolysis, loosening or presence of metallosis was evaluated with standard radiographs. Metallosis was evaluated intraoperatively according to the metallosis severity classification.

Results

The mean time from failure until revision surgery was 9.4 years. It was observed that in the primary THA, metal-on-ceramic (MoC), ceramic-on-ceramic (CoC) and metal-on-conventional polyethylene (MoCPE) bearings were used in 1, 3 and 11 hips, respectively. Grade III metallosis was observed in all patients during revision surgeries. The mean Harris hip score increased from 55 points before revision THA to 75 points at the final follow-up. In revision arthroplasty, MoCPE and CoC bearings were used in 13 and 2 hips, respectively. The femoral stem was replaced in 5 hips. All acetabular cups, except that of one hip, were revised.

Conclusions

Revisions of THAs with catastrophic failures and metallosis are quite challenging. Routine follow-up of arthroplasty patients is beneficial to examine for osteolysis, loosening, and asymmetric wear.

Pseudotumors in Total Joint Arthroplasty

»

The true incidence of pseudotumors in association with total joint arthroplasty is underestimated.

»

Pseudotumors occur with metal-on-metal, metal-on-polyethylene, and metal-on-ceramic articulations.

»

Metal ion levels should not be the only factor in decision-making regarding revision surgery.

»

Revision surgery is only indicated in symptomatic patients with clinical and radiographic findings and elevated metal ion levels.

»

Revision to a non-metal articulation is strongly suggested.

Is there a relation between clinical scores and serum ion levels after MoM-THA? One year results in 383 implants

BACKGROUND AND AIM OF THE WORK

Adverse reaction to metal debris is the major cause of the high revision rates of metal on metal hip implants with femoral head size ≥ 36mm. Health authorities recommend regular surveillance even for asymptomatic individuals. The main investigations used are Co+ and Cr+ serum levels, x-rays and, eventually, ultrasound and MARS-MRI. Clinic is also assessed. The aim of this study is to identify if there is a relation between  ion levels and the clinical scores  in order to evaluate the outcome and  plan the correct management after this type of implant.

METHODS

383 subjects were included and divided in 3 groups (serum ion levels >, <  and >60 µg/L). Co+, Cr+, HHS and OHS results of 1 2017 were analysed in order to show a correlation between ion levels and clinical scores .

RESULTS

Clinical scores were similar in group 1 and 2. Differences were observed comparing the group 1 and 2 with group 3 for both variables.

DISCUSSION AND CONCLUSIONS

Surveillance algorithms have been introduced by health  authorities. Nevertheless, the indication to revision surgery is not simple especially in those cases in which a discrepancy between clinic and investigations is present. In this study clinical scores seem to be less important than ion levels in the evaluation of outcomes and in order to plan the correct management in the majority of cases. Larger studies are needed to highlight the real importance of clinical scores in the decision making after these type of implants.

MARS MRI Characteristics of Adverse Local Tissue Reactions in Taper Corrosion of Metal-On-Polyethylene THA Differ From Metal-On-Metal THA

BACKGROUND

Metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) has been recommended as a cross-sectional imaging modality in clinical evaluation of adverse local tissue reactions (ALTRs) in metal-on-metal (MoM) patients and metal-on-polyethylene (MoP) patients with taper corrosion. The aim of the study was to compare MARS MRI characteristics of ALTR in MoM total hip arthroplasty (THA) with ALTR in MoP THA with modular taper corrosion.

METHODS

A total of 197 patients with ALTR were evaluated: 86 patients with MoM THA; 37 MoP patients with head-neck taper corrosion; and 74 MoP patients with neck-stem dual taper corrosion. MARS MRI scans were evaluated to identify location, size, type of ALTR (I-III), and associated ALTR synovitis (cystic, solid, and mixed).

RESULTS

MARS MRI characteristics of ALTR were significantly different between the MoM and MoP groups (P = .017). The MoP group demonstrated the highest proportion of thick-walled cystic masses type II (56.7% in head-neck taper corrosion MoP and 46.5% in dual taper corrosion MoP vs 28.7% in MoM), whereas the MoM group had the highest proportion of thin-walled cystic masses type I. MoM implants (96.8%) were significantly more likely to have ALTR in multiple locations compared with both MoP groups (P = .001).

CONCLUSION

This study demonstrates that MARS MRI characteristics of ALTR differ by bearing type with a significantly higher percentage of mixed type and solid type ALTR in the taper corrosion MoP THA compared with MoM THA. This information provides clinically useful information in evaluation of symptomatic MoP and MoM THA patients for ALTRs.

What are the results of revised hip resurfacing arthroplasties?

Aims

Hip resurfacing arthroplasty (HRA) is typically indicated for young and active patients. Due to the longevity of arthroplasty, these patients are likely to undergo revision surgery during their lifetime. There is a paucity of information on the long-term outcome of revision surgeries performed after failed HRA. The aim of our study was to provide survivorship data as well as clinical scores after HRA revisions.

Methods

A total of 42 patients (43 hips) were revised after HRA at our centre to a variety of devices, including four HRA and 39 total hip arthroplasties (THAs). In addition to perioperative complications, University of California, Los Angeles (UCLA) hip scores and 12-Item Short-Form Health Survey questionnaire (SF-12) quality of life scores were collected at follow-up visits after the primary HRA and after revision surgery.

Results

The mean follow-up time after revision surgery was 8.3 years (0.3 to 19.1). The mean UCLA pain and function scores post-revision were comparable with the best scores achieved by the patients after the index HRA, but UCLA activity scores were lower after revision. SF-12 physical component scores were comparable between timepoints, but the mental component score decreased after revision. Six patients underwent unilateral re-revision surgery at a mean follow-up time of 7.8 years (0.3 to 13.7). Using the time to any re-revision as endpoint, the Kaplan-Meier survivorship was 85.3% at 13 years.

Conclusion

Patients undergoing revision after HRA can expect to achieve function and quality of life similar to their best after their primary surgery, while the risk of re-revision is low. Cite this article: Bone Joint J 2020;102-B(10):1289–1296.

Results of hydroxyapatite ceramic coated primary femoral stem in revision total hip replacement

PURPOSE

The purpose of this study was to assess survival rate, functional and radiological outcomes when using a hydroxyapatite-ceramic fully coated primary femoral stem in revision total hip arthroplasty.

METHODS

Patients who underwent revision total hip arthroplasty using the Furlong hydroxyapatite-ceramic (HAC)-coated (Joint Replacement Instrumentation Ltd., Sheffield, UK) primary stem were retrospectively identified between 2013 and 2017. A total of 30 hips in 27 patients were identified and the mean follow-up duration was 44 months. Post-operative radiographs were scrutinized for signs of component loosening by two independent assessors. Patient's functional outcomes were assessed using the Oxford hip score and compared pre- and post-operatively. The prevalence of thigh pain was assessed at the latest follow-up.

RESULTS

The most common cause of revision was adverse reactions to metal debris (ARMD) (46.6%). The overall complication rate was 13.3%. Results at final follow-up demonstrated 100% survival rate and no reported incidence of thigh pain. Using paired t test, all patients had a statistically significant (P < 0.05) improvement in post-operative mean Oxford hip score of 35 compared to a mean pre-operative score of 14. Radiographic analysis of the latest follow-up radiographs revealed no signs of component loosening or component subsidence.

CONCLUSION

With a 100% survival rate and excellent reported functional outcomes, we believe that our experience and results support the use of primary cementless stems in selected revision cases.

Complications and re-revisions after revisions of 528 metal-on-metal hips because of adverse reaction to metal debris

Background and purpose - There is limited amount of evidence about optimal revision indications, technique, and implants when performing revision surgery for metal-on-metal (MoM) hip replacements due to adverse reaction to metal debris (ARMD). We assessed which factors are related to re-revisions and complications after a revision of MoM hip arthroplasty because of ARMD. We also aimed to provide information on optimal implants for these revisions.Patients and methods - 420 MoM total hip arthroplasties (THA) and 108 MoM hip resurfacings were implanted and later revised at our institution. We used Cox regression to analyze the factors associated with re-revisions and complications after a revision for ARMD.Results - A re-revision was performed on 27 THAs (6%) and 9 resurfacings (8%). The most common indication for re-revision was recurrent dislocation (20 hips, 4%). Complications not leading to re-revision were seen in 21 THAs (5%) and 6 resurfacings (6%). The most common complication was dislocation treated with closed reduction in 13 hips (2%). Use of revision head size > 36mm was associated with decreased risk for dislocations. Presence of pseudotumor, pseudotumor grade, pseudotumor size, or the choice of bearing couple were not observed to affect the risk for re-revision. Non-linear association was observed between preoperative cobalt and risk for re-revision.Interpretation - As dislocation was the most frequent post-revision complication, large head sizes should be used in revisions. Because size or type of pseudotumor were not associated with risk of re-revision, clinicians may have to reconsider, how much weight is put on the imaging findings when deciding whether or not to revise. In our data blood cobalt was associated with risk for re-revision, but this finding needs further assessment.

Revision of a dual-modular stem in patients with adverse tissue reaction

BACKGROUND

Dual-modular femoral components with exchangeable cobalt-chrome neck segments have had higher than expected failure rates due to corrosion and adverse local tissue reaction (ALTR). Complications, survival rates and early clinical outcomes of revision surgery for the treatment of corrosion and ALTR as a result of these implants are underreported.

METHODS

We identified 44 cases of revision THA for corrosion and ALTR resulting from the same dual modular stem. All revision procedures were performed using a modular tapered fluted titanium stem, ceramic heads and highly cross-linked polyethylene.

RESULTS

Complications included: dislocation, infection, reoperation, and chronic pain. Mean Harris Hip Score was 84 following revision surgery.

CONCLUSIONS

Patients undergoing revision surgery for ALTR related to this prosthesis should be aware of the risk of postoperative dislocation and other complications and the potential long-term risk of some chronic pain.

Clinical Results of Revision Hip Arthroplasty for Neck-Taper Corrosion and Adverse Local Tissue Reactions Around a Modular Neck Stem

BACKGROUND

Adverse local tissue reactions (ALTRs) around a modular neck stem at our institution lead to a 13.5% rate of revision. The purpose of this study was to report the clinical results of revision total hip arthroplasty (THA) in this patient population.

METHODS

We identified 80 hips in 77 patients who underwent revision THA due to neck-stem corrosion. Intraoperative and postoperative complications, clinical outcomes, re-revision rates, and the postoperative ion levels were recorded.

RESULTS

The mean follow-up period after revision was 45.3 ± 16.3 months (range 24-81 months). There were no intraoperative mechanical complications during the revision surgery. Eight hips (10%) had postoperative complications related to the revision implant, of which 6/8 came to re-revision: postoperative implant dislocation in 4 hips-2 treated nonsurgically, aseptic loosening of femoral component in 2 hips, and periprosthetic femoral fracture in 2 hips. No patients had recurrence of ALTR nor the recurrence of groin pain within the follow-up period. With 2 exceptions, ion levels normalized within one year of the revision surgery. The survival rate was 94% (95% confidence interval 84-98) at 32 months and 82% (95% confidence interval 56-93) at 63 months after revision THA (using re-revision THA due to any reason as the endpoint).

CONCLUSION

Intraoperative complication, postoperative complication, and re-revision rates are equivalent to femoral revision surgeries for other causes (infection, fracture, loosening). We recommend selecting revision-type stems to minimize the risk of femoral loosening or periprosthetic fracture, and larger femoral heads or dual mobility bearings to minimize the risk of dislocation.

Radiographic evaluation of hip resurfacing: the role of x-rays in the diagnosis of a problematic resurfaced hip

INTRODUCTION

Hip resurfacing (HRA) requires a new standardised radiographic evaluation protocol. Evaluation of acetabular components is similar to total hip arthroplasty (THA) but femoral components require different criteria. This study evaluates the efficacy of a new femoral zonal system for radiographic HRA assessment in identifying clinical problems.

METHODS

A new proximal femoral zonal system divides implant-cement-bone interfaces at head and neck into 7 DeSmet zones. 611 in situ and 100 revised HRA were assessed for component positioning, borderline findings (reactive lines, cortical thickening, cancellous condensation) or sinister findings (lucent lines, bone resorption, osteolysis). Findings were correlated with gender, size, implant survival, clinical scores, metal ions, and adverse soft tissue reactions (ALTR).

RESULTS

Radiological changes were found in 265 hips (37.3%), 154 sinister (21.7%) and 111 borderline (15.6%). 84% of revisions had sinister findings versus 11.4% of in situ HRA (p < 0.001). The mean number of abnormal acetabular and femoral zones was 3.3 in revised compared to 0.6 in situ HRA (p < 0.001). Sinister findings were associated with female gender, lower clinical scores, smaller sizes or ASR design (all: p < 0.001). Metal ions were higher with sinister (p < 0.001) and borderline (p < 0.01) findings compared to normal radiographs. Pathological findings in ⩾4 zones had a sensitivity of 50% and specificity of 94.2% (AUC = 0.898) in detecting hips with ALTR (odds ratio = 49).

CONCLUSION

In order to accurately evaluate progressive radiographic changes in HRA, specific zones have been established around the femoral component. There was a high correlation between radiographic findings and outcome measures. 84% of problematic hips and 90.4% of proven ALTR had sinister changes.

Superior patient reported outcome measures reported post Articular Surface Replacement (ASR) revision arthroplasty in the setting of an objective surgical indication

The Articular Surface Replacement (ASR) hip system displayed unexpectedly high failure rates. All patients who underwent revision arthroplasty at our institution were identified. Indications for revision were classified as objectively identifiable or performed for unexplained pain. Clinical outcomes, post ASR revision, were superior in cases where the aetiology for failure was identifiable. Pain and function improved reliably when a targeted objective indication was identified pre-revision, but failed to do so in cases of unexplained pain. Surgeons familiar with the results of this study will be empowered to discuss expectations and realistic outcomes with their patients undergoing complex revision arthroplasty cases.

Dual Mobility for Monoblock Metal-on-Metal Revision-Is It Safe?

BACKGROUND

Revision of monoblock metal-on-metal (MoM) total hip arthroplasty (THA) is associated with high complication rates. Limited revision by conversion to a dual mobility (DM) without acetabular component extraction may mitigate these complications. However, the concern for polyethylene wear and osteolysis remains unsettled. This study investigates the results of DM conversion of monoblock MoM THA compared to formal acetabular revision.

METHODS

One hundred forty-three revisions of monoblock MoM THA were reviewed. Twenty-nine were revisions to a DM construct, and 114 were complete revisions of the acetabular component. Mean patient age was 61, 54% were women. Components used, acetabular cup position, radiographic outcomes, serum metal ion levels, and HOOS Jr clinical outcome scores were investigated.

RESULTS

At 3.9 years of follow-up (range 2-5), there were 2 revisions (6.9%) in the DM cohort, 1 for instability and another for periprosthetic fracture. Among the formal acetabular revision group there was a 20% major complication rate (23/114) and 16% underwent revision surgery (18/114) for aseptic loosening of the acetabular component (6%), deep infection (6%), dislocation (4%), acetabular fracture (3%), or delayed wound healing (6%). In the DM cohort, there were no radiographic signs of aseptic loosening, component migration, or polyethylene wear. One DM patient had a small posterior metadiaphyseal femur lesion that will require close monitoring. There were no other radiographic signs of osteolysis. There were no clinically significant elevations of serum metal ion levels. HOOS Jr scores were favorable.

CONCLUSION

Limited revision with conversion to DM is a viable treatment option for failed monoblock MoM THA with lower complication rates than formal revision. Limited revision to DM appears to be a safe option for revision of monoblock MoM THA with a cup in good position and an internal geometry free of sharp edges or articular surface damage. Longer follow-up is needed to demonstrate any potential wear implications of these articulations.

Revision total hip arthroplasty for metal-on-metal failure

Metal-on-metal (MoM) arthroplasty systems became popular in the early-2000s due to presumed advantages of improved wear characteristics and superior stability. However, subsequent reports of abnormal soft-tissue reactions to MoM implants and national registry data reporting high failure rates raised concerns. Early outcomes of revision total hip arthroplasty (THA) for adverse reaction to metal debris (ARMD) were poor, leading to development of surveillance programs and a trend towards early revision surgery. Patients with MoM arthroplasties require surveillance, comprehensive history and physical examination, imaging with ultrasound or magnetic resonance imaging (MRI), and laboratory evaluation including metal ion levels. Operative strategies for revision THA vary from exchange of modular components to extensive debridement and reconstruction with revision components. Surgeons should be aware of the increased risks of dislocation and infection following revision THA for ARMD. However, there is growing evidence that early revision surgery prior to extensive soft tissue destruction results in improved outcomes and decreased re-operation rates. It is estimated that >1 million MoM articulations have been implanted, with a large proportion still in situ. It is imperative to understand the aetiology, presentation, and management strategies for these patients to optimise their clinical outcomes.

Follow-up of Metal-on-Metal Hip Replacements at a Large District Hospital and the Implementation of Medicines and Healthcare Products Regulatory Agency Guidelines: A Review of 297 Patients

Background

Medicines and Healthcare products Regulatory Agency (MHRA) guidance for patients with metal-on-metal (MoM) hip replacements was provided in 2012 and updated in 2017 to assist in the early detection of soft-tissue reactions due to metal wear debris. A large number of MoM hip replacements were undertaken at our hospital trust. A program of recall for all patients with MoM hip replacements was undertaken and MHRA guidelines were implemented. In this study, we aimed to investigate the effectiveness of the revised MHRA guidelines in the detection of early adverse reactions to metal debris and to re-evaluate the indications for metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) and revision surgery.

Methods

Identification and recall of all patients with MoM hip replacements from 2001 were conducted by using theatre logs, patient records, clinical coding information, and consultant logbooks. Two senior arthroplasty consultants reviewed X-rays and patient records. Postal questionnaires were forwarded to patients, together with requests for general practitioners to complete cobalt and chromium blood tests. The two consultant-led review of MOM replacements was undertaken with further radiological investigations (X-rays, MARS-MRI) performed according to the 2017 guidance with support of consultant radiologists.

Results

Of 674 identified patients, 297 were available for review: 26 patients did not have MoM implants, 36 were untraceable, 59 refused follow-up, 87 moved out of area, 147 had died, and 22 already had revision. Of 297 patients, 126 were women and 171 were men; age range was 39 to 95 years (mean age, 69 years); 126 had resurfacing and 171 had MoM replacements. Twenty-six patients had elevated metal ions. Thirty-three patients underwent MARS-MRI: MARS-MRI results were positive in 17 and negative in 16. Of 17 patients with positive MARS-MRI, 10 patients were asymptomatic and seven were waiting revision.

Conclusions

Positive MARS-MRI can often occur in the absence of elevated metal ion levels; elevated blood metal ion levels do not mean MARS-MRI will be positive. All patients with MoM replacements were at risk. It is imperative to assess patients regularly for symptoms that may raise clinical suspicion and maintain a low threshold to performing MARS-MRI.

Has the threshold for revision surgery for adverse reactions to metal debris changed in metal-on-metal hip arthroplasty patients? A cohort study of 239 patients using an adapted risk-stratification algorithm

Background and purpose - A risk-stratification algorithm for metal-on-metal hip arthroplasty (MoMHA) patients was devised by US experts to help clinicians make management decisions. However, the proposed algorithm did not cover all potential patient or surgical abnormalities. Therefore we adapted the US risk-stratification algorithm in MoMHA patients revised for adverse reactions to metal debris (ARMD) to determine the variability in the revision threshold, and also whether high-risk patients had inferior outcomes following revision.Patients and methods - We analysed 239 MoMHA revisions for ARMD between 2001 and 2016 from 2 centres with pre-revision blood metal ions and imaging. Patients were stratified (low risk, moderate risk, high risk) using pre-revision factors (implant, radiographic, blood metal ions, cross-sectional imaging) by adapting a published algorithm. The risk categories for each factor were assessed against revision year, revision centre, and post-revision outcomes (re-revision surgery, and any poor outcome).Results - Compared with hips revised before 2012, hips revised from 2012 onwards included more high-risk implants (44% vs. 17% pre-2012), high-risk radiographic features (85% vs. 69% pre-2012), and low-risk metal ions (41% vs. 19% pre-2012). 1 centre more frequently revised patients with high-risk implants (48% vs. 14%) and low-risk blood metal ions (45% vs. 15%) compared with the other. All these comparisons were statistically significant (p < 0.05). With the limited sample size available, implant, radiographic, blood metal ion, and cross-sectional imaging risk groups did not statistically significantly affect the rates of re-revision surgery or frequency of poor outcomes post-revision.Interpretation - When applying the adapted risk-stratification algorithm the threshold for ARMD revision changed over time, presumably due to increasing evidence, patient surveillance, and investigation since 2012. Lower blood metal ion thresholds were used from 2012 for ARMD revisions; however, there was evidence that centres attached different importance to metal ions when managing patients. High-risk patients did not have inferior outcomes following ARMD revision.

Femoral Fixation Methods in Hip Resurfacing Arthroplasty: An 11-Year Retrospective Comparison of 4013 Cases

BACKGROUND

The optimal femoral fixation method remains unclear. To evaluate the role of femoral fixation techniques in hip resurfacing, we present a comparison of 2 consecutive groups: group 1 (739 hips) with cemented femoral components; group 2 (3274 hips) with uncemented femoral components.

METHODS

We retrospectively analyzed our clinical database to compare failures, reoperations, complications, clinical results, and radiographic measurements. Groups were consecutive, so cemented cases had longer follow-up. However, all patients from both groups were at least 2 years out from surgery. Two-year clinical and radiographic data were compared. Longer-term comparison data as well as Kaplan-Meier implant survivorship curves specifically focusing on femoral failure modes were analyzed.

RESULTS

Kaplan-Meier 10-year implant survivorship using nontraumatic femoral failure as an end point was 98.9% for the cemented and 100% for the uncemented femoral component. The uncemented, group 2 cases showed a significantly lower raw failure rate (1.1% vs 4.6%), 2-year failure rate (0.8% vs 2.8%), 2-year femoral failure rate (0.4% vs 0.9%), and a lower combined rate of femoral complications and failures (0.6% vs 1.8%). In cases that did not fail, patient mean clinical scores, pain scores, and combined range of motion were all significantly better for group 2.

CONCLUSION

We have demonstrated that in the fully porous-coated ReCap device, uncemented femoral fixation is superior to cemented fixation at 11 years follow-up (0.0% vs 1.1% late femoral loosening) in this single-surgeon cohort. Early femoral fractures also reduced from 0.8% to 0.3%, but this may be partially or completely due to a new bone density management program. This study demonstrates better femoral implant survivorship for the uncemented device compared to the cemented femoral resurfacing component for this implant design.

Conversion of Hip Resurfacing With Retention of Monoblock Acetabular Shell Using Dual-Mobility Components

BACKGROUND

Retention of the acetabular component is an option during conversion from hip resurfacing arthroplasty (HRA) to total hip arthroplasty (THA). The purpose of this study was to compare clinical outcomes of conversion of the femoral resurfacing component with retained acetabular components (RAC) and use of dual-mobility femoral heads to outcomes of patients treated with both component (BC) revisions.

METHODS

A retrospective review was performed of the clinical outcomes of HRA to THA conversions performed at a single institution between 2008 and 2017.

RESULTS

Seventy-one conversions were included (27 RAC and 44 BC). Average age at time of conversion was 54.4 years (range, 30-68 years). Median time to conversion was 5.14 (2.77-7.41) years and median follow-up post-conversion was 1.7 (0.33-4.0) years. There were no significant differences in indications for conversion between the 2 groups with the majority performed for complications related to elevated metal ions and aseptic loosening. Harris Hip Scores improved from pre-conversion to post-conversion in both cohorts (P < .01). There were no significant differences in pre-conversion and post-conversion metal ion levels between the RAC and BC groups. Serum metal ion levels decreased significantly in both cohorts (P < .01). There were 6 additional revisions in the cohort (4 in BC, 2 in RAC) at a median 2.94 (1.99-3.85) years post-conversion. Two RAC patients had intraprosthetic dislocations with extensive polyethylene wear requiring acetabular revision at median 3.92 (3.85-3.98) years post-conversion. Overall, there were a higher number of complications in the BC group related to acetabular fracture, failure of osseointegration, and periprosthetic joint infection; however, this did not reach statistical significance (P = .27).

CONCLUSION

Salvage of an appropriately positioned, well-fixed HRA acetabular component is a reasonable option in the setting of conversion to THA using dual-mobility components. This technique avoids the morbidity of acetabular revision and was associated with a decrease in metal ion levels and improvements in short-term functional outcomes comparable to a BC revision.

Revision of Failed Metal-on-Metal Total Hip Arthroplasty: Midterm Outcomes of 203 Consecutive Cases

BACKGROUND

Metal-on-metal (MoM) revisions have shown high rates of complications from aseptic loosening, deep infection, and dislocation. The purpose of this study is to report on outcomes and complications of a large consecutive series of patients who were revised for failed MoM total hip arthroplasty (THA).

METHODS

We evaluated 188 patients (203 hips) who underwent revisions of failed MoM THA. Mean age at the revision was 60 years old. Gender was female in 112 hips (55%) and male in 91 hips (45%). Mean interval to failure after primary THA was 4.9 years (range, 0-18 years). The acetabular component was revised in 183 cases (92%). Clinical outcomes assessed included pain score and Harris hip score.

RESULTS

Mean follow-up from revision was 4.2 years. Harris hip score improved from 53.6 pre-revision to 73.5 at most recent follow-up (P < .001). Pain level significantly improved from 17.2 pre-revision to 32.8 post-revision (P < .001). Reoperations occurred in 28 (14%) hips. Re-revision was required in 16 hips (7.9%). The most common reasons for re-revision were aseptic loosening (5), dislocation (3), infection (2), and iliopsoas tendonitis (2). Re-revision was significantly higher in cases of pseudotumor. There was no difference in survival with ultraporous cups. Three hips required re-revision to custom triflange components. All-cause survival was 90.5% at 4.2 years. Metal ion levels significantly declined after revision.

CONCLUSION

Revisions of failed MoM THA showed improvements in clinical outcomes, but present significant surgical challenges and complications especially in cases with soft tissue damage and pseudotumor.

No Threshold Exists for Recommending Revision Surgery in Metal-on-Metal Hip Arthroplasty Patients With Adverse Reactions to Metal Debris: A Retrospective Cohort Study of 346 Revisions

BACKGROUND

Surgeons currently have difficulty when managing metal-on-metal hip arthroplasty (MoMHA) patients with adverse reactions to metal debris (ARMD). This stems from a lack of evidence, which is emphasized by the variability in the recommendations proposed by different worldwide regulatory authorities for considering MoMHA revision surgery. We investigated predictors of poor outcomes following MoMHA revision surgery performed for ARMD to help inform the revision threshold and type of reconstruction.

METHODS

We retrospectively studied 346 MoMHA revisions for ARMD performed at 2 European centers. Preoperative (metal ions/imaging) and intraoperative (findings, components removed/implanted) factors were used to predict poor outcomes. Poor outcomes were postoperative complications (including re-revision), 90-day mortality, and poor Oxford Hip Score.

RESULTS

Poor outcomes occurred in 38.5%. Shorter time (under 4 years) to revision surgery was the only preoperative predictor of poor outcomes (odds ratio [OR] = 2.12, confidence interval [CI] = 1.00-4.46). Prerevision metal ions and imaging did not influence outcomes. Single-component revisions (vs all-component revisions) increased the risk of poor outcomes (OR = 2.99, CI = 1.50-5.97). Intraoperative modifiable factors reducing the risk of poor outcomes included the posterior approach (OR = 0.22, CI = 0.10-0.49), revision head sizes ≥36 mm (vs <36 mm: OR = 0.37, CI = 0.18-0.77), ceramic-on-polyethylene revision bearings (OR vs ceramic-on-ceramic = 0.30, CI = 0.14-0.66), and metal-on-polyethylene revision bearings (OR vs ceramic-on-ceramic = 0.37, CI = 0.17-0.83).

CONCLUSION

No threshold exists for recommending revision in MoMHA patients with ARMD. However postrevision outcomes were surgeon modifiable. Optimal outcomes may be achieved if surgeons use the posterior approach, revise all MoMHA components, and use ≥36 mm ceramic-on-polyethylene or metal-on-polyethylene articulations.

Is end-organ surveillance necessary in patients with well-functioning metal-on-metal hip resurfacings?

Aims

Cardiac magnetic resonance (CMR) was used to assess whether cardiac function or tissue composition was affected in patients with well-functioning metal-on-metal hip resurfacing arthroplasties (MoMHRA) when compared with a group of controls, and to assess if metal ion levels correlated with any of the functional or structural parameters studied.

Patients and Methods

In all, 30 participants with no significant cardiac history were enrolled: 20 patients with well-functioning MoMHRA at mean follow-up of 8.3 years post-procedure (ten unilateral, ten bilateral; 17 men, three women) and a case-matched control group of ten non-MoM total hip arthroplasty patients (six men, four women). The mean age of the whole cohort (study group and controls) at the time of surgery was 50.6 years (41.0 to 64.0). Serum levels of cobalt and chromium were measured, and all patients underwent CMR imaging, including cine, T2* measurements, T1 and T2 mapping, late gadolinium enhancement, and strain measurements.

Results

None of the MoMHRA patients showed clinically significant cardiac functional abnormality. The MoMHRA patients had larger indexed right and left end diastolic volumes (left ventricular (LV): 74 ml/m2 vs 67 ml/m2, p = 0.045; right ventricular: 80 ml/m2 vs 71 ml/m2, p = 0.02). There was a small decrease in T2 time in the MoMHRA patients (median 49 ms vs 54 ms; p = 0.0003). Higher metal ion levels were associated with larger LV volumes and with shorter T2 time.

Conclusion

Although cardiac function is not clinically adversely affected in patients with well-functioning MoMHRA, modern imaging is able to demonstrate subtle changes in structure and function of the heart. As these changes correlate with systemic ion measurements, they may be consequences of wear debris deposition. Longer, longitudinal studies are necessary to determine whether cardiac function will become affected. Cite this article: Bone Joint J 2019;101-B:540–546.

Perioperative factors associated with increased length of stay after revision of metal-on-metal total hip arthroplasty

Objective

To investigate patient factors influencing length-of-stay (LOS) after revision metal-on-metal (MoM) total hip arthroplasty (THA).

Methods

We reviewed 23 hips undergoing revision of a MoM THA with minimum 2-year follow-up. A multiple linear regression was calculated to predict LOS using multiple variables.

Results

Average length of stay (LOS) was 2.1 days. Multiple linear regression analysis identified a significant correlation between presence of an abductor injury (beta = 0.8886; p < 0.0001), patient age (beta = -0.4452, p = 0.0083), and pre-revision head size (beta = 0.4082; p = 0.0172) with LOS (R² = 0.6351, p = 0.0002).

Conclusion

Patients with abductor injury, larger femoral heads, and younger age are at risk for longer LOS.

Origins of material loss in highly worn acetabular cups of metal-on-metal total hip replacements

Excessive wear has been one of the major failure modes of metal-on-metal hip implants. From a collection of 541 retrieved ASR metal-on-metal implants, we selected those head-cup pairs with combined wear >100 mm³ , (N = 42) to assess the distributions of wear volume on cups, and non-conformance in the worn areas at the head-cup interfaces. All 42 had severe cup edge wear (average maximum wear depth 500 μm). On average, 58% of wear volume of cups occurred at the edge areas, whereas 42% occurred well inside the socket, indicating that substantial wear volume of cups was generated well inside the socket. Particularly, in eight cups, more than half of the wear volume occurred well inside the socket. The head-cup conformance in the worn areas was deteriorated. On average, in worn areas, head-cup clearance was approximately eight times greater than in unworn areas, and the sphericity of heads and cups was approximately 36 times and 84 times higher, respectively, than in unworn areas. The radius of curvature of the worn surfaces of heads and cups varied widely, with an average variation of 3 mm (0.6-7 mm) and 11 mm (2-47 mm) for heads and cups, respectively. The severely deteriorated conformance at the edge areas and the areas well inside the socket, due to edge contact, could be the major factor for excessive wear of these 42 pairs. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.